High speed buses such as the Gunning Transceiver Logic Plus (GTL+) bus (Pentium Pro Family Developers Manual, Volume 1 Specification, published 1996) require the use of resistors at the physical ends of its electrical traces to properly terminate the bus. The resistors provide an electrical pull-up function and act as a lumped impedance load to minimize signal reflections off the ends of the traces. If a GTL+ bus is operated with only one end of its traces terminated, the reliability of the computer system in which it is implemented in can be severely degraded. While a computer system may seem to be operating normally with an improperly terminated GTL+ bus, it is possible for data to be irreversibly corrupted without warning.
The Pentium.RTM. II processor incorporates GTL+ bus termination resistors within the Single Edge Connector (SEC) cartridge enclosing the processor. A computer system designed to use two Pentium II processors is designed with the Slot 1 connectors located at the physical ends of each GTL+ bus trace. Therefore, when two processors are installed in a dual Slot 1 system, each trace on the GTL+ bus is properly terminated via the termination resistors in the SEC cartridges, and reliable system operation is assured.
While a computer system may be designed to accommodate two Pentium II processors, reliable system operation with only one processor installed is possible with the use of a termination card. A termination card is a circuit board with a gold finger edge connector which mates with a Slot 1 connector. A termination card contains the necessary pull-up/termination resistors to properly terminate GTL+ bus signals. A termination card may be installed in a Slot 1 connector in place of a processor to provide the pull-up and termination normally supplied by the second SEC cartridge. The termination card must be installed in the unused Slot 1 connector to maintain the design quality of the signals on the GTL+ bus. Without it, system operation may be unreliable.